Blower apparatus

ABSTRACT

This blower apparatus includes an air blowing portion including a plurality of flat plates arranged with an axial gap defined between adjacent ones of the flat plates; a motor portion arranged to rotate the air blowing portion; and a housing arranged to house the air blowing portion and the motor portion. The housing includes an air inlet and an air outlet. At least one of the flat plates is defined by a non-perfect circular flat plate having an outer edge configuration in which specific configurations repeatedly appear one after another in a circumferential direction in a plan view. Once the air blowing portion starts rotating, an air flow traveling radially outward is generated between the flat plates by viscous drag of surfaces of the flat plates and a centrifugal force.

BACKGROUND OF THE INVENTION 1. Field Of the Invention

The present invention relates to a blower apparatus.

2. Description of the Related Art

A centrifugal blower apparatus which generates an air flow traveling radially outward by rotating an impeller including a plurality of blades is known. A known blower apparatus including an impeller is described in, for example, JP-A 2008-88985.

In the blower apparatus described in JP-A 2008-88985, a plurality of blades referred to as fan blades push surrounding gas to generate air flows traveling radially outward.

SUMMARY OF THE INVENTION

In recent years, there has still been a demand for reductions in the size and thickness of electronic devices. Accordingly, there has also been a demand for a reduction in the thickness of blower apparatuses used to cool the interiors of the electronic devices.

Here, in the case where an impeller is used to generate air flows, as in the blower apparatus describe in JP-A 2008-88985, air flows pushed by a blade leak from axially upper and lower ends of the blade while the impeller is rotating. As a result, air pressure is lower at the axially upper and lower ends of the blade than in the vicinity of an axial middle of the blade. Accordingly, a reduction in the thickness of the blower apparatus, involves a reduction in the axial dimension of the impeller, will result n a failure to secure sufficient air blowing efficiency.

In addition, there has been a demand for a reduction in noise, in addition to a reduction in thickness, of blower apparatuses installed in electronic devices or the like.

An object of the present invention is to provide a technique for achieving a reduction in noise of a centrifugal blowing apparatus which is excellent in air blowing efficiency.

A blower apparatus according to a preferred embodiment of the present invention includes an air blowing portion arranged to rotate about a central axis extending in a vertical direction; a motor portion arranged to rotate the air blowing portion; and a housing arranged to house the air blowing portion and the motor portion. The housing includes an air inlet arranged above the air blowing portion, and arranged to pass through a portion of the housing in an axial direction; and an air outlet arranged to face in a radial direction at at least one circumferential position radially outside of the air blowing portion. The air blowing portion includes a plurality of flat plates arranged in the axial direction with an axial gap defined between adjacent ones of the flat plates. At least one of the flat plates is defined by a non-perfect circular flat plate having an outer edge configuration in which specific configurations repeatedly appear one after another in a circumferential direction in a plan view.

According to the above preferred embodiment of the present invention, once the air blowing portion starts rotating, an air flow traveling radially outward is generated in the axial gap between the adjacent ones of the flat plates by viscous drag of surface of the flat plates and a centrifugal force. Thus, gas supplied through the air inlet and an air hole travels radially outwardly he air blowing portion. Since the air flow is generated between the flat plates, the air flow does not easily leak upwardly or downwadly, and thus, an improvement in air blowing efficiency is achieved. Accordingly, a reduced thickness of the blower apparatus according to the above preferred embodiment of the present invention does not result in a significant reduction in the air blowing efficiency. In addition, the blower apparatus according to the above preferred embodiment of the present invention is superior to a comparable centrifugal fan including an impeller in terms of being silent. With the at least one of the flat plates being defined by a non-perfect circular flat plate, small eddies are intentionally generated in air flows in the vicinity of an outer edge portion(s) of the flat plate(s) to achieve an additional redaction in noise.

The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a blower apparatus according to a first preferred embodiment of the present invention.

FIG. 2 is a top view of the blower apparatus according to the first preferred embodiment.

FIG. 3 is a sectional view of the blower apparatus according to the first preferred embodiment.

FIG. 4 is an exploded perspective view of the blower apparatus according to the first preferred embodiment.

FIG. 5 is a partial sectional view of the blower apparatus according to the first preferred embodiment.

FIG. 6 is a top view of a plurality of flat plates of the blower apparatus according to the first preferred embodiment.

FIG. 7 is a top view of a plurality of flat plates of a blower apparatus according to a modification of the first preferred embodiment.

FIG. 8 is a partial sectional view of a blower apparatus according to a modification of the first preferred embodiment.

FIG. 9 is a top view of a blower apparatus according to a modification of the first preferred embodiment.

DETAILED DESCRIPTION OF TEE PREFERRED EMBODIMENTS

Hereinafter, blower apparatuses according to preferred embodiments of the present invention will be described. It is assumed herein that a side on which an upper plate portion is arranged with respect to a lower plate portion is upper side, and the shape of each member or portion and relative positions of different members or portions will be described based on the above assumption. It should be noted, however, that the above definition of the upper and lower sides is not meant to restrict in any way the orientation of a blower apparatus according to any preferred embodiment of the present invention at the time of manufacture or when in use.

1. First Preferred Embodiment

1-1. Structure of Blower Apparatus

FIG. 1 is a perspective view of a blower apparatus 1 according to a first preferred embodiment of the present invention. FIG. 2 is a top view of the blower apparatus 1. FIG. 3 is a sectional view of the blower apparatus 1 taken along line A-A in FIG. 2. FIG. 4 is an exploded perspective view of the blower apparatus 1. FIG. 5 is a partial sectional view of the blower apparatus 1. The blower apparatus 1 is a centrifugal blower apparatus designed to generate an air flow traveling radially outward by rotating an air blowing portion 40. The blower apparatus 1 is, for example, installed in an electronic device, such as, for example, a personal computer, to cool an interior thereof. Note that blower apparatuses according to preferred embodiments of the present invention may be used for other purposes.

Referring to FIGS. 1 to 4, the blower apparatus 1 includes a housing 20, a motor portion 30, and the air blowing portion 40.

The housing 20 is a case arranged to house the motor portion 30 and the air blowing portion 40. The housing 20 includes a lower plate portion 21, a side wall portion 22, and an upper plate portion 23.

The lower portion 21 is arranged to define a bottom portion of the housing 20. The lower plate portion 21 is arranged to extend radially below the air blowing portion 40 to cover at least a portion of a lower side of the air blowing portion 40. In addition, the lower plate portion 21 is arranged to support the motor portion 30.

The side wall portion 22 is arranged to extend upward from the lower plate portion 21. The side wall portion 22 is arranged to cover a lateral side of the air blowing portion 40 between the lower plate portion 21 and the upper plate portion 23. In addition, the side wall portion 22 includes an air outlet 201 arranged to face in a radial direction at one circumferential position. In the present preferred embodiment, the lower plate portion 21 and the side wall portion 22 are defined integrally with each other. Note that the lower plate portion 21 and the side wall portion 22 may alternatively be defined by separate members.

The upper plate portions 23 is arranged to define a cover portion of the housing 20. The upper plate portion 23 is arranged to extend radially above the lower plate portion 21. In addition, the upper plate portion 23 includes an air inlet 202 arranged to pass therethrough in an axial direction. In other words, the upper plate portion 23 includes an inner edge portion 231 arranged to define the air inlet 202. The air inlet 202 is, for example, circular and is centered on a central axis 9 in a plan view.

The motor portion 30 is a driving portion arranged to rotate the air blowing portion 40. Referring to FIG. 5, the motor portion 30 includes a stationary portion 31 and a rotating portion 32. The stationary portion 31 is fixed to the lower plate portion 21. The stationary portion 31 is thus arranged to be stationary relative to the housing 20. The rotating portion 32 is supported to be rotatable about the central axis 9 with respect to the stationary portion 31.

The stationary portion 31 includes a stator fixing portion 311, a stator 312, and a bearing housing 313.

The stator fixing portion 311 is fitted in a fixing hole 211 defined in the lower plate portion 21. As a result, the stator fixing portion 311 is fixed to the lower plate portion 21. The stator fixing portion 311 is arranged to extend upward from the fixing hole 211 to assume a cylindrical shape with the central axis 9 as a center thereof. The stator 312 is fixed to an outer circumferential portion of an upper portion of the stator fixing portion 311.

The stator 312 is an armature arranged to generate magnetic flux in accordance with electric drive currents supplied from an external source. The stator 312 is arranged to annularly surround the central axis 9, which extends in a vertical direction. The stator 312 includes, for example, an annular stator core defined by laminated steel sheets, and conducting wires wound around the stator core.

The bearing housing 313 is a member being cylindrical and having a closed bottom. Specifically, the bearing housing 313 includes a disk-shaped bottom portion, and a cylindrical portion arranged to extend upward from the bottom portion. The bearing housing 313 is fixed to an inner circumferential surface of the stator fixing portion 311.

The rotating portion 32 includes a shaft 321, a hub 322, a bearing member 323, and a magnet 324.

The shaft 321 is a member arranged to extend along the central axis 9. The shaft 321 according to the present preferred embodiment includes a columnar portion arranged inside of a first cylindrical portion 512, which will be described below, and arranged to extend with the central axis 9 as a center thereof, and a disk-shaped portion arranged to extend radially from a lower end portion of the columnar portion.

The hub 322 is fixed to the shaft 321. The hub 322 is made up of a hub body member 51 and a flange member 52.

The hub body member 51 includes a first top plate portion 511, the first cylindrical portion 512, a second cylindrical portion 513, and a magnet holding portion 514.

The first top plate portion 511 is a disk-shaped portion arranged to extend radially with the central axis 9 as a center therof. The first top plate portion 511 is arranged above the stator 312. The first top plate portion 511 has a recessed portion 515 recessed from an upper surface thereof at an outer edge portion thereof.

The first cylindrical portion 512 is arranged to extend downward from the first top plate portion 511 to assume a cylindrical shape with the central axis 9 as a center thereof. The columnar portion of the shaft 321 is housed in the first cylindrical portion 512. In addition, the shaft 321 is fixed to the first cylindrical portion 512.

The second cyclindrical portion 513 is arranged to extend downward from the first top plate portion 511 to assume a cylindrical shape with the central axis 9 as a center thereof. The second cylindrical portion 513 is arranged to have an inside diameter greater than an outside diameter of the first cylindrical portion 512. In other words, the second cyclindrical portion 513 is arranged radially outside of the first cylindrical portion 512.

The magnet holding portion 514 is arranged to extend downward from a radially outer edge of the first top plate portion 511 to assume a cylindrical shape with the central axis 9 as a center thereof. The magnet holding portion 514 is arranged radially outside of the stator 312. The magnet 324 is fixed to an inner circumferential surface of the magnet holding portion 514.

The flange member 52 includes an outer wall portion 521, a second top plate portion 522, and a flat plate holding portion 523.

The outer wall portion 521 is a cylindrical portion arranged to extend in the vertical direction with the central axis 9 as a center thereof. The outer wall portion 521 is arranged to extend along an outer circumferential surface of the magnet holding portion 514 of the hub body member 51.

The second top plate portion 522 is arranged to extend radially inward from an upper end portion of the outer wall portion 521 to assume the shape of a circular ring. The second top plate portion 522 is arranged in the recessed portion 515, which is defined in the upper surface of the first top plate portion 511 of the hub body member 51. In addition, the upper surface of the first top plate portion 511 and an upper surface of the second top plate portion 522 are arranged at the same axial position.

The flat plate holding portion 523 is arranged to extend radially outward from a lower end portion of the outer wall portion 521. The flat plate holding portion 523 is arranged to hold the air blowing portion 40 on a radially outer side of the magnet holding portion 514 of the hub body member 51. In the present preferred embodiment, the air blowing portion 40 is mounted on an upper surface of the flat plate holding portion 523. The flat plate holding portion 523 is thus arranged to hold a plurality of flat plates 410 included in the air blowing portion 40.

The bearing member 323 is a cylindrical member arranged to extend in the vertical direction with the central axis 9 as a center thereof. The bearing member 323 is arranged to extend along an outer circumferential surface of the first cylindrical portion 512 of the hub body member 51. In addition, the bearing member 323 is fixed to the outer circumferential surface of the first cylindrical portion 512. The cylindrical portion of the bearing housing 313 is arranged radially outside of the bearing member 323 and radially inside of the second cylindrical portion 513 of the hub body member 51.

The magnet 324 is fixed to the inner circumferential surface of the magnet holding portion 514 of the hub body member 51. In addition, the magnet 324 is arranged radially outside of the stator 312. The magnet 324 according to the present preferred embodiment is in the shape of a circular ring. A radially inner surface of the magnet 324 is arranged radially opposite to the stator 312 with a slight gap therebetween. In addition, an inner circumferential surface of the magnet 324 includes north and south poles arranged to alternate with each other in a circumferential direction. Note that a plurality of magnets may be used in place of the magnet 324 in the shape of a circular ring. In the case where the plurality of magnets are used, the magnets are arranged in the circumferential direction such that north and south poles of the magnets alternate with each other.

As illustrated in an enlarged view in FIG. 5, a lubricating fluid 300 is arranged between the bearing housing 313 and a combination of the shaft 321, the bearing member 323, and the hub body member 51. A polyolester oil or a diester oil, for example, is used as the lubricating fluid 300. The shaft 321, the hub 322, and the bearing member 323 are supported to be rotatable with respect to the bearing housing 313 through the lubricating fluid 300. Thus, in the present preferred embodiment, the bearing housing 313, which is a component of the stationary portion 31, the combination of the shaft 321, the bearing member 323, and the hub body member 51, each of which is a component of the rotating portion 32, and the lubricating fluid 300 together define a fluid dynamic bearing.

A surface of the lubricating fluid 300 is defined in a seal portion 301, which is a gap between an outer circumferential surface of the bearing housing 313 and an inner circumferential surface of the second cylindrical portion 513 of the hub body member 51. In the seal portion 301, the distance between the outer circumferential surface of the bearing housing 313 and the inner circumferential surface of the second cylindrical portion 513 is arranged to increase with decreasing height. In other words, in the seal portion 301, the distance between the outer circumferential surface of the bearing housing 313 and the inner circumferential surface of the second cylindrical portion 513 is arranged to increase with increasing distance from the surface of the lubricating fluid 300. Since the radial width of the seal portion 301 thus increases with decreasing height, the lubricating fluid 300 is attracted upward in the vicinity of the surface of the lubricating fluid 300. This reduces the likelihood that the lubricating fluid 300 will leak out of the seal portion 301.

Use of the fluid dynamic bearing as a bearing mechanism that connects the stationary portion 31 and the rotating portion 32 allows the rotating portion 32 to rotate stably. Thus, the likelihood of an occurrence of an unusual sound from the motor portion 30 can be reduced.

Once electric drive currents are supplied to the stator 312 in the motor portion 30 as described above, magnetic flux is generated around the stator 312. Then, interaction between the magnetic flux of the stator 312 and magnetic flux of the magnet 324 produces a circumferential torque between the stationary portion 31 and the rotating portion 32, so that the rotating portion 32 is caused to rotate about the central axis 9 with respect to the stationary portion 31. The air blowing portion 40, which is held by the flat plate holding portion 523 of the rotating portion 32, is caused to rotate about the central axis 9 together with the rotating portion 32.

Referring to FIGS. 4 and 5, the air blowing portion 40 includes the plurality of flat plates 410 and a plurality of spacers 420. The flat plates 410 and the spacers 420 are arranged to alternate with each other in the axial direction. In addition, adjacent ones of the flat plates 410 and the spacers 420 are fixed to each other through, for example, adhesion.

Referring to FIGS. 4 and 5, in the present preferred embodiment, the flat plates 410 include a top flat plate 411, which is arranged at the highest position, a bottom flat plate 412, which is arranged at the lowest position, and four intermediate flat plates 413, which are arranged below the top flat plate 411 and above the bottom flat plate 412. That is, the number of flat plates 410 included in the air blowing portion 40 according to the present preferred embodiment is six. The flat plates 410 are arranged in the axial direction with an axial gap 400 defined between adjacent ones of the flat plates 410.

Each flat plate 410 is made of, for example, a metal material, such as stainless steel, or a resin material. Each flat plate 410 may alternatively be made of, for example, paper. In this case, paper including a glass fiber, a metal wire, or the like in addition to plant fibers may be used. The flat plate 410 is able to achieve higher dimensional accuracy when the flat plate 410 is made of a metal material than when the flat plate 410 is made of a resin material.

In the present preferred embodiment, each of the top flat plate 411 and the four intermediate flat plates 413 is arranged to have the same shape and size. Referring to FIGS. 1, 2, and 5, each of the top flat plate 411 and the intermediate flat plates 413 includes an inner annular portion 61, an outer annular portion 62, a plurality of ribs 63, and a plurality of air holes 60. In the present preferred embodiment, the number of ribs 63 and the number of air holes 60 included in each of the top flat plate 411 and the intermediate flat plates 413 are both five. Each air hole 60 is arranged to be in communication with a space radially outside of the air blowing portion 40 through the axial gap(s) 400 adjacent to the flat plate 410 including the air hole 60 on the upper and/or lower sides of the flat plate 410. Each air hole 60 is arranged at a position overlapping with the air inlet 202 of the housing 20 when viewed in the axial direction.

The bottom flat plate 412 is an annular and plate-shaped member centered on the central axis 9. The bottom flat plate 412 has a central hole 65 arranged to pass therethrough in the vertical direction in a center thereof. The shape of each flat plate 410 will be described in detail below.

Referring to FIG. 4, each spacer 420 is a member in the shape of a circular ring. The spacers 420 are arranged between the flat plates 410 to secure the axial gaps 400 between the flat plates 410. Each spacer 420 has a central hole 429 arranged to pass therethrough in the vertical direction in a center thereof. The motor portion 30 is arranged in the central holes 65, which will be described below, of the flat plates 410 and the central holes 429 of the spacers 420.

Each spacer 420 is arranged at a position axially coinciding with the inner annular portion 61 of each of the top flat plate 411 and the intermediate flat plates 413. Thus, the spacer 420 is arranged in a region in the corresponding axial gap 400, the region covering only a portion of the radial extent of the corresponding axial gap 400.

Once the motor portion 30 is driven, the air blowing portion 40 is caused to rotate together with the rotating portion 32. As a result, viscous drag of a surface of each flat plate 410 and a centrifugal force together generate an air flow traveling radially outward in the vicinity of the surface of the flat plate 410. Thus, an air flow traveling radially outward is generated in each of the axial gaps 400 between the flat plates 410. Thus, gas above the housing 20 is supplied to each axial gap 400 through the air inlet 202 of the housing 20 and the air holes 60 of the top flat plate 411 and the intermediate flat plates 413, and is discharged out of the blower apparatus 1 through the air outlet 201, which is defined in a side portion of the housing 20.

Here, each flat plate 410 is arranged to have an axial thickness of about 0.1 mm. Meanwhile, each axial gap 400 is arranged to have an axial dimension of about 0.3 mm. The axial dimension of the axial gap 400 is preferably in the range of 0.2 mm to 0.5 mm. An excessively large axial dimension of the axial gap 400 would lead to a separation between an air flow generated by a lower surface of the flat plate 410 on the upper side and an air flow generated by an upper surface of the flat plate 410 on the lower side during rotation of the air blowing portion 40. This separation could result in a failure to generate sufficient static pressure in the axial gap 400 to discharge a sufficient volume of air. Moreover, an excessively large axial dimension of the axial gap 400 would make it difficult to reduce the axial dimension of the blower apparatus 1. Accordingly, in this blower apparatus 1, the axial dimension of the axial gap 400 is arranged to be in the range of 0.2 mm to 0.5 mm. This arrangement allows the blower apparatus 1 to achieve a reduced thickness while allowing an increase in the static pressure in the axial gap 400 to discharge a sufficient volume of air.

In addition, referring to FIG. 2, the air inlet 202 is centered on the central axis 9. That is, a center of the air inlet 202 coincides with the central axis Meanwhile, the air blowing portion 40 is also centered on the central axis 9. Accordingly, differences in pressure do not easily occur at different circumferential positions in the air blowing portion 40. This contributes to reducing noise. It is assumed that the term “coincide”as used here includes not only “completely coincide” but also “substantially coincide”.

1-2. Shapes of Flat Plates

Next, the shape of each flat plate 410 will now be described in detail below with reference to FIGS. 4 and 6. FIG. 6 is a top view of the flat plates 410.

Referring to FIG. 4, in the present preferred embodiment, each of the top flat plate 411 and the four intermediate flat plates 413 is arranged to have the same shape and size. As described above, each of the top flat plate 411 and the intermediate flat plates 413 includes the inner annular portion 61, the outer annular portion 62, the plurality of ribs 63, and the plurality of air holes 60.

The inner annular portion 61 is an annular portion centered on the central axis 9. The inner annular portion 61 has the central hole 65 arranged to pass therethrough in the vertical direction in a center thereof. The outer annular portion 62 is an annular portion arranged radially outside of the inner annular portion 61 with the central axis 9 as a center thereof. Each rib 63 is arranged to join the inner annular portion 61 and the outer annular portion 62 to each other. Each air hole 60 is arranged to pass through the flat plate 410 in the axial direction. Each air hole 60 is surrounded by the inner annular portion 61, the outer annular portion 62, and two circumferentially adjacent ones of the ribs 63.

In a related-art blower apparatus that generates air flows by rotating an impeller including a plurality of blades, air flows generated by the impeller leak at upper and lower end portions of the impeller. This leakage of the air flows occurs regardless of the axial dimension of the blower apparatus. Therefore, as the blower apparatus is designed to be thinner, an effect of this leakage on the blower apparatus as a whole becomes greater, resulting in lower air blowing efficiency. Meanwhile, in the blower apparatus 1 according to the present preferred embodiment, the air flows are generated in the vicinity of the surfaces of the flat plates 410, and therefore, the air flows do not easily leak upward or downward. Therefore, even when the axial dimension of the air blowing portion 40, which generates the air flows, is reduced, a reduction in air blowing efficiency due to leakages of the air flows does not easily occur. That is, even when the blower apparatus 1 has a reduced thickness, a reduction in air blowing efficiency thereof does not easily occur.

In addition, in a blower apparatus including an impeller, periodic noise occurs owing to the shape, number, arrangement, and so on of blades. However, this blower apparatus 1 is superior to a comparable blower apparatus including an impeller in terms of being silent, because the air flows are generated by the viscous drag of the surface of each flat plate 410 and the centrifugal force in the blower apparatus 1.

In addition, from the viewpoint of P-Q characteristics (i.e., flow rate-static pressure characteristics), the blower apparatus 1 including the flat plates 410 is able to produce a higher static pressure in a low flow rate region than the blower apparatus including the impeller. Therefore, when compared to the blower apparatus including the impeller, the blower apparatus 1 is suitable for use in a densely packed case, from which only a relatively small volume of air can be discharged. Examples of such cases include cases of electronic devices, such as, for example, personal computers.

In the present preferred embodiment, the top flat plate 411 and all the intermediate flat plates 413 include the air holes 60. Accordingly, all the axial gaps 400 are in axial communication with a space above the housing 20 through the air inlet 202 and the air holes 60.

Each of the top flat plate 411 and the intermediate flat plates 413 includes the air holes 60. Accordingly, in each of the top flat plate 411 and the intermediate flat plates 413, the outer annular portion 62, which is arranged radially outside of the air holes 60, defines an air blowing region which generates an air flow in the vicinity of a surface thereof. Meanwhile, the bottom flat plate 412 includes no air hole 60. Therefore, in an upper surface of the bottom flat plate 412, an entire region radially outside of a portion of the bottom flat plate 412 which makes contact with the spacer 420 defines an air blowing region. In other words, in the upper surface of the bottom flat plate 412, a region which axially coincides with the air holes 60 and the ribs 63 of the top flat plate 411 and the intermediate flat plates 413, and a region which axially coincides with the outer annular portions 62 thereof, together define the air blowing region. In addition, in a lower surface of the bottom flat plate 412, an entire region radially outside of a portion of the bottom flat plate 412 which makes contact with the flat plate holding portion 523 defines an air blowing region. Notice that an air flow is generated by a lower surface of the flat plate holding portion 523 as well.

As described above, the bottom flat plate 412 has air blowing regions wider than the air blowing regions of the top flat plate 411 and the intermediate flat plates 413. Therefore, the axial gap 400 between the lowest one of the intermediate flat plates 413 and the bottom flat plate 412 is able to have higher static pressure than any other axial gap 400.

Air flows passing downward through the air inlet 202 and the air holes 60 are drawn radially outward in each axial gap 400. Therefore, the air flows passing through the air holes 60 become weaker as they travel downward. In the present preferred embodiment, the bottom flat plate 412 is arranged to have an air blowing region wider than the air blowing regions of the top flat plate 411 and the intermediate flat plates 413 to cause a stronger air flow to be generated in the lowest one of the axial gaps 400 than in any other axial gap 400 to cause the air flows passing downward through the air holes 60 to be drawn toward the lowest axial gap 400. Thus, a sufficient volume of gas is supplied to the lowest axial gap 400 as well. As a result, the air blowing portion 40 achieves improved air blowing efficiency.

Referring to FIG. 6, each of the flat plates 410 is defined by a non-perfect circular flat plate having an outer edge configuration in which specific configurations 71 repeatedly appear one after another in the circumferential direction in a plan view. Here, the term “specific configuration” refers to a configuration different from a curve in the shape of a circular arc centered on the central axis 9. In addition, the wording “specific configurations repeatedly appear” means that the outer edge configuration includes three or more specific configurations. When at least one of the flat plates 410 has the specific configurations 71 as described above, small eddies are intentionally generated in air flows in the vicinity of an outer edge portion(s) of the flat plate(s) 410. This contributes to preventing a large eddy from occurring in an air flow. This in turn contributes to preventing an occurrence of noise due to an eddy in an air flow. Thus, an additional reduction in noise of the blower apparatus 1 can be achieved.

In this blower apparatus 1, each flat plate 410 includes an outer edge in the shape of a regular tridecagon. That is, each flat plate 410, which is defined by a non-perfect circular flat plate, includes an outer edge in the shape of a polygon. Thus, each specific configuration 71 includes straight portions 711 and an angled portion 712. Since the flat plate 410 is in the shape of a polygon, the specific configuration is defined by a simple combination of straight lines. This eliminates the need to perform a complicated molding process, which would be required if the specific configuration were a configuration including a non-straight line, such as, for example, a cut, a complicated curved shape, or a combination of a plurality of shapes, to achieve a reduction in noise. Moreover, the area of the regular tridecagon is about 96% of the area of a circle having the same maximum diameter. Therefore, the flat plate 410 having an outer edge configuration in the shape of a regular tridecagon is able to achieve a reduction in noise without causing a significant reduction in area of the air blowing region when compared to a flat plate having an outer edge configuration in the shape of a circle with the same maximum diameter.

In each flat plate 410, the specific configurations 71 are arranged at regular intervals in the circumferential direction. It is assumed here that the wording “regular intervals” includes “substantially regular intervals”. The periodic arrangement of the specific configurations 71 contributes to maintaining an excellent weight balance of the flat plate 410. Thus, the flat plate 410 is able to stably rotate. This leads to an additional reduction in noise.

The number of specific configurations 71 included in each flat plate 410 is thirteen, which is a prime number. Depending on the number of specific configurations 71, a peak of noise occurs at a different frequency corresponding to a natural frequency thereof. When the number of specific configurations 71 is not a prime number, peaks of noise occur at frequencies corresponding to all divisors thereof. In this blower apparatus 1, the number of specific configurations 71 is a prime number, and therefore, a peak occurs only at a frequency corresponding to that number, reducing the number of peaks that occur. That is, an additional reduction in noise can be achieved. The number of specific configurations 71 included in each flat plate 410 may alternatively be another prime number, such as, for example, five, seven, or eleven.

In this blower apparatus 1, a motor with twelve poles and nine slots is used as the motor portion 30. Therefore, the number of specific configurations 71 included in each flat plate 410 is prime to each of the number of slots of the motor portion 30 and the number of poles of the motor portion 30. In addition, in this blower apparatus 1, the number of ribs 63 included in each of the top flat plate 411 and the intermediate flat plates 413 is five. Therefore, the number of specific configurations 71 included in each flat plate 410 is prime to the number of ribs 63. This contributes to preventing noise that occurs due to the specific configurations 71 from resonating with noise that occurs due to the motor portion 30 and the ribs 63. Thus, an additional reduction in noise can be achieved.

2. Example Modifications

While a preferred embodiment of the present invention has been described above, it is to be understood that the present invention is not limited to the above-described preferred embodiment.

FIG. 7 is a top view of a plurality of flat plates 410A of a blower apparatus according to a modification of the above-described preferred embodiment. In the blower apparatus according to the modification illustrated in FIG. 7, each of the flat plates 410A is defined by a non-perfect circular flat plate having an outer edge configuration in which specific configurations 71A repeatedly appear one after another in the circumferential direction in a plan view. In addition, each specific configuration 71A includes a cut 713A recessed radially inward. A known rotating body or high-speed propeller is sometimes provided with an uneven surface in the form of sawteeth called a serration to cause colliding air flows to be diffused to achieve a reduction in noise. In this flat plate 410A, the cuts 713A serve as a serration to achieve a reduction in noise of the blower apparatus.

In addition, in the blower apparatus according to the modification illustrated in FIG. 7, the flat plates 410A are arranged to rotate to one side in the circumferential direction along with rotation of a motor portion 30A. A portion of the outer edge configuration of each flat plate 410A which defines each cut 713A includes a cut guide portion 714A arranged to curve to an opposite side in the circumferential direction as it extends radially outward. Thus, the cut guide portion 714A extends along a direction of an air flow that passes near a surface of the flat plate 410A. This contributes to preventing an air flow from being disturbed near the cut guide portion 714A. This leads to an improvement in air blowing efficiency of the blower apparatus.

Referring to FIG. 7, each of ribs 63A is arranged to curve to the opposite side in the circumferential direction as the rib 63A extends radially outward. As a result, the rib 63A extends along a direction of an air flow that passes near the surface of the flat plate 410A. This contributes to preventing the rib 63A from disturbing the air flow near the flat plate 410A. This leads to an improvement in the air blowing efficiency of the blower apparatus. In addition, a curvature of each cut guide portion 714A and a curvature of each rib 63A are arranged to be equal to each other. It is assumed here that the term “equal” includes “substantially equal”. This contributes to more effectively preventing each of the cuts 713A and the ribs 63A from causing a significant reduction in the air blowing efficiency.

FIG. 8 is a partial sectional view of a blower apparatus 1B according to another modification of the above-described preferred embodiment. In the blower apparatus 1B according to the modification illustrated in FIG. 8, a motor portion 30B includes a stationary portion 31B, a rotating portion 32B, and two ball bearings 33B.

The stationary portion 31B includes a stator fixing portion 311B and a stator 312B. The stator fixing portion 311B is a member being cylindrical and having a closed bottom and fixed to a housing 20B. The stator 312B is an armature fixed to an outer circumferential surface of the stator fixing portion 311B.

The rotating portion 32B includes a shaft 321B, a hub 322B, and a magnet 324B. At least a lower end portion of the shaft 321B is arranged inside of the stator fixing portion 311B. In addition, an upper end portion of the shaft 321B is fixed to the hub 322B. The magnet 324B is fixed to the hub 322B. The magnet 324B is arranged radially opposite to the stator 312B.

Each ball bearing 333 is arranged to connect the rotating portion 32B to the stationary portion 31B such that the rotating portion 32B is rotatable with respect to the stationary portion 31B. Specifically, an outer race of each ball bearing 33B is fixed to an inner circumferential surface of the stator fixing portion 311B of the stationary portion 31B. In addition, an inner race of each ball bearing 33B is fixed to an outer circumferential surface of the shaft 321B of the rotating portion 32B. Further, a plurality of balls, each of which is a spherical rolling element, are arranged between the outer race and the inner race. As described above, instead of a fluid dynamic bearing, rolling-element bearings, such as, for example, ball bearings, may be used as a bearing structure of the motor portion 30B.

In the modification illustrated in FIG. 8, the motor portion 30B includes the two ball bearings 33B. The ball bearings 33B are arranged near an upper end and a lower end of an axial range over which the inner circumferential surface of the stator fixing portion 311B and the shaft 321B are opposed to each other. This contributes to preventing the shaft 321B from being inclined with respect to a central axis 9B.

FIG. 9 is a top view of a blower apparatus 1C according to yet another modification of the above-described preferred embodiment. In the blower apparatus 1C according to the modification illustrated in FIG. 9, a housing 20C includes a plurality of air outlets 201C. Specifically, a side wall portion 220 includes the air outlets 201C, each of which is arranged to face in a radial direction, at a plurality of circumferential positions. The housing 20C includes tongue portions 203C, each of which is arranged near a separate one of the air outlets 201C. In addition, an air blowing portion 40C includes a plurality of flat plates 410C arranged in the axial direction with an axial gap defined between adjacent ones of the flat plates 410C.

In a centrifugal fan including an impeller, periodic noise occurs owing to the shape, number, arrangement, and so on of blades. In addition, such noise tends to easily occur around a tongue portion. Accordingly, when air is to be discharged in a plurality of directions, a deterioration in noise characteristics occurs because of an increased number of tongue portions. However, in this blower apparatus 1C, air flows traveling radially outward are generated by rotation of the flat plates 410C, and therefore, the blower apparatus 1C is able to achieve reduced periodic noise when compared to the centrifugal fan including the impeller. Therefore, the blower apparatus 1C, which is designed to discharge air in a plurality of directions, does not significantly deteriorate in noise characteristics due to the tongue portions 203C.

Note that, although the number of flat plates included in the air blowing portion is six in each of the above-described preferred embodiment and the modifications thereof, this is not essential to the present invention. The number of flat plates may alternatively be two, three, four, five, or more than six.

Also note that, although the hub is defined by two members, i.e., the hub body member and the flange member, in each of the above-described preferred embodiment and the modifications thereof, this is not essential to the present invention. The hub may alternatively be defined by a single member, or three or more members.

Also note that the detailed shape of any member may be different from the shape thereof as illustrated in the accompanying drawings of the present application. For example, the shape of any of the housing, the air blowing portion, and the motor portion may be different from that according to each of the above-described preferred embodiment and the modifications thereof. Also note that features of the above-described preferred embodiment and the modifications thereof may be combined appropriately as long as no conflict arises.

Preferred embodiments of the present invention are applicable to blower apparatuses.

While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims. 

What is claimed is:
 1. A blower apparatus comprising: an air blowing portion arranged to rotate about a central axis extending in a vertical direction; a motor portion arranged to rotate the air blowing portion; and a housing arranged to house the air blowing portion and the motor portion; wherein the housing includes: an air inlet arranged above the air blowing portion, and arranged to pass through a portion of the housing in an axial direction; and an air outlet arranged to face in a radial direction at at least one circumferential position radially outside of the air blowing portion; the air blowing portion includes a plurality of flat plates arranged in the axial direction with an axial gap defined between adjacent ones of the flat plates; and at least one of the flat plates is defined by a non-perfect circular flat plate having an outer edge configuration in which specific configurations repeatedly appear one after another in a circumferential direction in a plan view.
 2. The blower apparatus according to claim 1, wherein each specific configuration includes a cut recessed radially inward.
 3. The blower apparatus according to claim 2, wherein the air blowing portion is caused by the motor portion to rotate to one side in the circumferential direction; and a portion of the outer edge configuration which defines the cut includes a cut guide portion arranged to curve to an opposite side in the circumferential direction as the cut guide portion extends radially outward.
 4. The blower apparatus according to claim 3, wherein each non-perfect circular flat plate includes: an inner annular portion being annular, and centered on the central axis; an outer annular portion being annular, centered on the central axis, and arranged radially outside of the inner annular portion; a plurality of ribs each of which is arranged to radially join the inner annular portion and the outer annular portion to each other; and a plurality of air holes each of which is surrounded by the inner annular portion, the outer annular portion, and two circumferentially adjacent ones of the ribs, and is arranged to pass through the non-perfect circular flat plate in the axial direction; each air hole is arranged to be in communication with a space radially outside of the air blowing portion through the axial gap; each rib is arranged to curve to the opposite side in the circumferential direction as the rib extends radially outward; and a curvature of the cut guide portion and a curvature of the rib are arranged to be equal to each other.
 5. The blower apparatus according to claim 1, wherein each specific configuration includes an angled portion; and the non-perfect circular flat plate includes an outer edge in a shape of a polygon.
 6. The blower apparatus according to claim 1, wherein, a number of specific configurations included in the non-perfect circular flat plate is a prime number.
 7. The blower apparatus according to claim 1, wherein, in the non-perfect circular flat plate, the specific configurations are arranged at regular intervals in the circumferential direction.
 8. The blower apparatus according to claim 1, wherein a center of the air inlet is arranged to coincide with the central axis.
 9. The blower apparatus according to claim 1, wherein the motor portion includes: a stationary portion including an armature and a bearing housing; and a rotating portion including a shaft, a bearing member, and a magnet arranged radially opposite to the armature; the bearing housing and a combination of the shaft and the bearing member are arranged to have a lubricating fluid therebetween; the bearing housing and the rotating portion are arranged to together define a gap defining a seal portion therebetween, the seal portion having a surface of the lubricating fluid defined therein; and in the seal portion, a distance between the bearing housing and the rotating portion is arranged to increase with increasing distance from the surface of the lubricating fluid.
 10. The blower apparatus according to claim 1, wherein the motor portion includes: a stationary portion including an armature; a rotating portion including a magnet arranged radially opposite to the armature; and a ball bearing arranged to connect the rotating portion to the stationary portion such that the rotating portion is rotatable with respect to the stationary portion.
 11. The blower apparatus according to claim 1, wherein the housing includes a plurality of the air outlets at a plurality of circumferential positions. 